The present invention relates to the field of door hinges. Specifically, it relates to door hinges used on the outer doors of commercial buildings.
The outer doors of a commercial building ordinarily do not have any latch to hold a door closed. Such doors are usually mounted on pivots and are controlled only by a door closing device which provides uniform or substantially uniform spring force to close the door. This force cannot be very high because it is essential that a person be able to push on the door without exerting great force to open it easily. However, the fact that the door must be designed to yield easily to a person pushing or pulling on it also means that it is easy for the wind to blow the door open; slamming it to its farthest opened position. This causes damage to the door, the door frame, and in extreme cases to adjacent glass panels.
The applicant by means of a unique and simple modification to the hinge structure of a door has created a door pivot which allows a door to operate under the control of a door closing device for most of its travel but will apply a very heavy progressive spring force to the door as it nears the wide open position. This allows the door to be brought to a gradual, rather than sudden, stop when an usually heavy force, like a blast of wind, causes the door open. This is an improvement over the conventional solutions to the problem of the door being violently swung open. This is because conventional solutions to this problem usually only increase the spring force directly against the door through its entire opening movement. However, that only makes the door more difficult to operate.
The applicant knows of no other prior art which has the same structure or functions in the same manner as his invention. For example, U.S. Pat. No. 4,377,019 (Takahashi), shows a vertical bar extending the full height of the door with a coil spring wrapped around it. However, the free end of the coil spring is attached to the door (or whatever is on the hinge) so the spring acts full time to impede the progress of the door rather than just before the farthest open position as does the applicant's invention. U.S. Pat. No. 2,309,279 (Smythe), likewise shows a spring that acts full time although its conical winding makes it stronger through part of its movement. The purpose is totally different from that of the applicant's invention in that the Smythe patent is not a true hinge but a device which moves partly around a pivot and partly in another direction so that the lamp globe can move against a gasket in a direction that does not distort the gasket. This is very different from the structure of the applicant's invention. U.S. Pat. No. 1,931,271 (Simmons), does show a spring that is effective at the end of the swing of the door. The door has a part 20 which is a half circle. The part strikes the flat spring 26. However, the Simmons patent does not show the principle on which the applicant's device operates nor does it show the same structure. U.S. Pat. No. 1,745,773 (Sipe), works on a similar principal to the Simmons patent. However Sipe has a strip 19 which is made of material like rubber which is designed to engage the inner wall 17a of the recess 17 thereby stopping the movement of the door. Both the Simmons patent and the Sipe patent are different in structure from the applicant's invention. They function as shock absorbers when the door is pushed open roughly. The applicant's invention functions as a shock preventer by gradually increasing the amount of force required to swing the door when it is most nearly open. As such the applicant's invention provides resistance to the door swinging open wildly by allowing low resistance when the door is just opened and having that resistance increased rapidly when the door almost reaches its maximum opening swing. The Simmons patent and the Sipe patent are designed to absorb the shock of a door that swings open suddenly. They do not provide increase resistance to the force that is pushing the door. Rather, they provide a means of absorbing the shock once the door has reached its maximum swing.
U.S. Pat. No. 3,538,539 (Allison), shows a door stop built into a hinge but there is no apparent resilience. There are several structures shown but in each case a fixed stop limits the motion of the door. The hinge pin can be moved to change the place at which the stop prevents further motion of the door but there is no spring. U.S. Pat. No. 3,178,762 (Whiting), appears to be similar to the Allison patent. There is a door stop but no proper spring. It should be noted that there is a frictional element which distorts the sleeve 12 as shown in FIGS. 2, 3, and 4 to give it a slight amount of spring. The purpose is not so much to bring the door to a gentle stop as it is to protect the life of the hinge.